Hadrian: fix windows cross-build (#20657)

Many small things to fix:

* Hadrian: platform triple is "x86_64-w64-mingw32" and this wasn't recognized by
  Hadrian (note "w64" instead of "unknown")

* Hadrian was using the build platform ("isWindowsHost") to detect
  the use of the Windows toolchain, which was wrong. We now use the
  "targetOs" setting.

* Hadrian was doing the same thing for Darwin so we fixed both at once,
  even if cross-compilation to Darwin is unlikely to happen afaik (cf
  "osxHost" vs "osxTarget" changes)

* Hadrian: libffi name was computed in two different places and one of
  them wasn't taking the different naming on Windows into account.

* Hadrian was passing "-Irts/include" when building the stage1 compiler
  leading to the same error as in #18143 (which is using make).
  stage1's RTS is stage0's one so mustn't do this.

* Hadrian: Windows linker doesn't seem to support "-zorigin" so we
  don't pass it (similarly to Darwin)

* Hadrian: hsc2hs in cross-compilation mode uses a trick (taken from
  autoconf): it defines "static int test_array[SOME_EXPR]" where
  SOME_EXPR is a constant expression. However GCC reports an error
  because SOME_EXPR is supposedly not constant. This is fixed by using
  another method enabled with the `--via-asm` flag of hsc2hs. It has been
  fixed in `make` build system (5f6fcf7808b16d066ad0fb2068225b3f2e8363f7)
  but not in Hadrian.

* Hadrian: some packages are specifically built only on Windows but they
  shouldn't be when building a cross-compiler (`touchy` and
  `ghci-wrapper`). We now correctly detect this case and disable these
  packages.

* Base: we use `iNVALID_HANDLE_VALUE` in a few places. It fixed some
  hsc2hs issues before we switched to `--via-asm` (see above). I've kept
  these changes are they make the code nicer.

* Base: `base`'s configure tries to detect if it is building for Windows
  but for some reason the `$host_alias` value is `x86_64-windows` in my
  case and it wasn't properly detected.

* Base: libraries/base/include/winio_structs.h imported "Windows.h" with
  a leading uppercase. It doesn't work on case-sensitive systems when
  cross-compiling so we have to use "windows.h".

* RTS: rts/win32/ThrIOManager.c was importin "rts\OSThreads.h" but this
  path isn't valid when cross-compiling. We replaced "\" with "/".

* DeriveConstants: this tool derives the constants from the target
  RTS header files. However these header files define `StgAsyncIOResult`
  only when `mingw32_HOST_OS` is set hence it seems we have to set it
  explicitly.
  Note that deriveConstants is called more than once (why? there is
  only one target for now so it shouldn't) and in the second case this
  value is correctly defined (probably coming indirectly from the import
  of "rts/PosixSource.h"). A better fix would probably be to disable the
  unneeded first run of deriveconstants.

4 files changed, 5 insertions, 4 deletions

diff --git a/libraries/base/GHC/Event/Windows.hsc b/libraries/base/GHC/Event/Windows.hsc
index a695df71d2..dd0b2d9db9 100644
--- a/libraries/base/GHC/Event/Windows.hsc
+++ b/libraries/base/GHC/Event/Windows.hsc
@@ -481,7 +481,7 @@ associateHandle' hwnd
 
 -- | A handle value representing an invalid handle.
 invalidHandle :: HANDLE
-invalidHandle = intPtrToPtr (#{const INVALID_HANDLE_VALUE})
+invalidHandle = iNVALID_HANDLE_VALUE
 
 -- | Associate a 'HANDLE' with the I/O manager's completion port.  This must be
 -- done before using the handle with 'withOverlapped'.
diff --git a/libraries/base/System/Environment/ExecutablePath.hsc b/libraries/base/System/Environment/ExecutablePath.hsc
index 6d8eac9b83..5cb49489c5 100644
--- a/libraries/base/System/Environment/ExecutablePath.hsc
+++ b/libraries/base/System/Environment/ExecutablePath.hsc
@@ -56,6 +56,7 @@ import Data.Word
 import Foreign.C
 import Foreign.Marshal.Array
 import Foreign.Ptr
+import GHC.Windows
 #include <windows.h>
 #include <stdint.h>
 #else
@@ -278,7 +279,7 @@ executablePath = Just (Just <$> getExecutablePath)
 getFinalPath :: FilePath -> IO FilePath
 getFinalPath path = withCWString path $ \s ->
   bracket (createFile s) c_closeHandle $ \h -> do
-    let invalid = h == wordPtrToPtr (#const (intptr_t)INVALID_HANDLE_VALUE)
+    let invalid = h == iNVALID_HANDLE_VALUE
     if invalid then pure path else go h bufSize
 
   where go h sz = allocaArray (fromIntegral sz) $ \outPath -> do
diff --git a/libraries/base/configure.ac b/libraries/base/configure.ac
index 68295563af..e034549476 100644
--- a/libraries/base/configure.ac
+++ b/libraries/base/configure.ac
@@ -12,7 +12,7 @@ AC_USE_SYSTEM_EXTENSIONS
 
 AC_MSG_CHECKING(for WINDOWS platform)
 case $host_alias in
-    *mingw32*|*mingw64*|*cygwin*|*msys*)
+    *mingw32*|*mingw64*|*cygwin*|*msys*|*windows*)
         WINDOWS=YES;;
     *)
         WINDOWS=NO;;
diff --git a/libraries/base/include/winio_structs.h b/libraries/base/include/winio_structs.h
index da9dab05b7..a4c7604fd0 100644
--- a/libraries/base/include/winio_structs.h
+++ b/libraries/base/include/winio_structs.h
@@ -4,7 +4,7 @@
  * Structures supporting the IOCP based I/O Manager or Windows.
  */
 
-#include <Windows.h>
+#include <windows.h>
 #include <stdint.h>
 
 #if defined(_WIN64)